4.3 Internal Resistor Ladder

The OPA module includes an internal resistor ladder, which can be configured to control the gain of the operational amplifier.

The internal resistor ladder can be used to provide feedback to the OPA module using the following configurations:

  • Set the RESON bit (RESON = 0b1).
  • Set the internal resistor ladder to the required value using the GSEL bits.
  • The NSS channel must be configured to connect the OPA inverting input source to the internal resistor ladder.
    • In non-inverting configurations, NSS is usually grounded to VSS (NSS = 0b111).
    • In inverting configurations, NSS is connected to a user selectable input (NSS = 0b0xx).
  • Set one of the input channels (NCH or PCH) to use the Internal Resistor Ladder (GSS), (NCH or PCH = 0b001).